The present invention relates to robots and more particularly to robot controls and velocity feedback systems for such controls.
The arm of an industrial robot is provided with a plurality of joints that are interconnected by links. Each joint is driven by a motor under the direction of the robot control. The robot tool tip is moved over commanded paths and/or to commanded positions through coordinated movement of the joints.
Robot controls normally have a control loop configuration that includes a velocity control for each joint motor. The velocity control loop employs joint motor velocity feedback typically generated by a tachometer or derived from position encoder output signals.
The operation of the robot arm is thus highly dependent on the validity of the velocity feedback. If the tachometer or encoder becomes defective or if velocity feedback otherwise becomes erroneous or lost, robot arm control is essentially lost and resultant arm motion could result in personal injury or property damage.
For safety and property protection reasons, it is thus desirable to provide a backup mechanism for monitoring the velocity feedback system in a robot control and providing protective action in the event a failure is detected. The referenced patent applications disclose a new completely digital robot control system in which velocity feedback control is employed. The present invention is directed to a backup velocity monitor and protection system embodied in that robot control.